The present invention relates in general to vehicle speed control units and in particular to an adjustable throttle connector for such a vehicle speed control unit.
Vehicle speed control units are widely known in the art and are adapted to maintain a vehicle at a constant predetermined speed despite varying engine loads, such as are imposed by the course of the road or the wind. Because of their reliability, accuracy, and inexpensiveness, fluid-actuated vehicle speed control units have become the dominant factor in the marketplace. Such speed control units typically utilize vacuum from the vehicle engine manifold as the actuating force. The vacuum is selectively supplied to a diaphragm connected to the engine throttle linkage, thereby increasing or decreasing the throttle position to increase or decrease engine power to maintain the vehicle speed. The control unit for such a system compares a signal representing the actual vehicle speed with a signal representing the desired vehicle speed and adjusts the vacuum level supplied to the diaphragm accordingly.
One problem encountered in utilizing vehicle speed control units of this type is that the total length of throttle travel from a fully closed position to a fully open position varies greatly from vehicle to vehicle, depending upon engine design. Thus, the size and stroke length of the vacuum diaphragm of the speed control unit must also vary from vehicle to vehicle in order to provide an efficient and responsive operation. For example, if a relatively short stroke vacuum diaphragm is utilized, the vehicle speed control unit will not be able to fully open the throttle of a long stroke linkage vehicle. On the other hand, if a relatively long stroke vacuum diaphragm is utilized, the vehicle speed control unit will make overly large throttle corrections when utilized on a short stroke linkage vehicle and may possibly damage the throttle linkage by attempting to open the throttle beyond its maximum position. Unfortunately, it is very costly and inefficient to provide a plurality of different vehicle speed control unit models, each adapted for use in a particular type of vehicle model or engine.